In a wireless communications system, a base station may carry an EPDCCH in a specific transmission resource, and send control information related to a carrier to a UE by sending the EPDCCH; correspondingly, the UE may also find the EPDCCH in the specific transmission resource, so as to obtain related configuration information of the carrier from the found EPDCCH by means of parsing.
Specifically, a base station determines an available EPDCCH resource set in a subframe, determines, according to an aggregation level of a to-be-transmitted EPDCCH and from the EPDCCH resource set, the number of and an allocation manner of candidates corresponding to the transmission of the aggregation level, places the to-be-transmitted EPDCCH in any candidate and sends the to-be-transmitted EPDCCH to a UE. Correspondingly, after obtaining information of the EPDCCH resource set, the UE may also determine, according to the same manner, the number of and an allocation manner of candidates corresponding to each aggregation level, and the UE may attempt to detect candidates of different aggregation levels separately, so as to obtain related control information of a carrier from a detected correct EPDCCH.
During implementation of the foregoing EPDCCH transmission, the inventor finds that the prior art has at least the following problems: when EPDCCHs of multiple carriers are sent in an EPDCCH resource set at the same time, an allocation manner of candidates for carrying the EPDCCHs is determined for each carrier by using a same algorithm, and therefore, distribution locations of EPDCCH candidates of any two carriers at the same aggregation level are completely the same, but an EPDCCH candidate can only carry one EPDCCH; as a result, some EPDCCHs at the same aggregation level are discarded, resulting in problems of EPDCCH blocking and unreliable transmission of control information.